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Need advice on chasing down a rattle on my m20.

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    Need advice on chasing down a rattle on my m20.

    This car keeps kicking my ass and decided to ask for some forum help not only in my build thread.

    I need to pinpoint this stupid rattle/knock in the engine I've been chasing for the past month an a half. I don't drive the car anymore because of it, only start it and warm it up once in a while after I change something.
    Engine is a freshly built 3.0 m20, everything I could afford is brand new. It has covered over 3000 kms now and just recently developed a noise that wasn't there.
    Here are some of the components built in, in case anyone can share some known issues with them

    Bottom end

    M20b27 1985 block
    Low mileage m54b30 crank and rods
    Low mileage m54b25 pistons, milled down for valve relief and CR
    Kolbenschmidt rings
    Brand new M21 oil pump
    IE crank scraper dremeled to fit the m54 crank and rods
    IE windage tray

    Head
    Slightly ported and polished 885 head
    M40 valves cut and polished to match the m20 valve height
    All new valve guides and seats (3 angle job on the seats)
    Dbilas 292o Camshaft with 11.2 mm lift (2mm clearance to piston, measured with clay prior assembly)
    Schrick dual valve springs
    Vac Motorsports spring perches/retainers (are they called perches?)
    Brand new rocker shafts
    IE HD rockers
    Brand new OEM eccentrics and hardware for them
    Brand new oil tube
    Nuke performance cam wheel (checked it for clearance to the bolts for the cam shaft seal - it clears)

    Here are the symptoms and what I've done so far:

    Symptoms:

    Rattle when engine running, rpm dependent, not movement or under load dependent. It is there even if cold started (cooled down overnight). NOT there when I start the car after 4 or more days of not driving it, but by the time I switch off the lights in the garage, close the door and lock it, get back into the car, the rattle is already there - quiet, but already there. It gets worse when the engine reaches operating temperature. It got progressively worse/louder over the course of about 10 days of driving after the last track day. I can hear it pronounced listening from the top of the engine, less pronounced from the bottom with the car on the lift, but still loud enough.
    On that trackday the oil DID get to the 150oC mark briefly, which is about 300oF, but the oil is now changed. Water temp never got over the middle mark.
    Oil pressure is 1.3-1.4 bar (18.8 psi - 20.3 psi) when idling on warmed up engine and always has been.

    The engine DOES have a windage tray and crank scraper.
    No noticeable power loss ( nor gains as well for that matter :D )

    What I've done so far:

    Oil change (flushed the oil cooler too) - didn't work
    Rocker arm eccentric to valve stem clearance adjustment TWICE - second time was on the engine 10 days not started, did them 0.25 - no change at all
    Inspected the oil tube over the rockers - clean, oil passes through, isn't low enough for the rockers to hit it.
    Checked as best as I could for rocker arm and eccentric premature wear (everything is brand new) - no visual issues
    Verified following twice: timing, bolt on cam sprocket, jeesus bolt and crank sprocket too - nothing out of order
    Cam sensor doesn't hit the trigger in place of the distributor.
    Cam belt tight enough, not slapping about
    Started engine without accessories belt - no change
    Unplugged coil connectors one by one while engine running to listen if the noise would change - no change
    Pressed gently against the clutch on warmed up engine - didn't feel it through the pedal.
    Listening with a screwdriver from the top I can hear it between cyl 2 and cyl 3, when listening from the bottom on the pan - almost everywhere. Not on the block though.
    Pulled the plugs, in order of appearance








    What I still haven't done yet:

    Compression test, but did one before this rattle emerged - average of 210 psi across all cylinders on a warm engine.
    Check the drive pulley on the oil drive shaft (it is a brand new unit, the solid one, not stamped steel one)
    Pull the pan and check bearing caps.

    A short video:

    https://vimeo.com/360510585

    So, if anyone has any input for me, highly appreciated.
    I'm waiting on a tiny camera with an LED to stuff into the cylinders right now. But would like to know if there is anything else I can check before pulling the pan off. Really don't want to do that, figured someone may have had similar experiences.

    Help, please
    '85 Alpine Weiß 2-door with m20b30 ground up build

    #2
    Does it go away when you push in the clutch pedal while not moving at idle?

    https://www.r3vlimited.com/board/for...ith-clutch-out

    Comment


      #3
      Did noise start after the high oil temp event?
      89 E30 325is Lachs Silber - currently M20B31, M20B33 in the works, stroked to the hilt...

      new build thread http://www.r3vlimited.com/board/showthread.php?t=317505

      Comment


        #4
        Originally posted by tim88325is View Post
        Does it go away when you push in the clutch pedal while not moving at idle?

        https://www.r3vlimited.com/board/for...ith-clutch-out
        No, I did this test a while ago and didn't notice any difference at all.

        Originally posted by digger View Post
        Did noise start after the high oil temp event?
        The noise started shortly after the high temp event,next day to be exact and got progressively worse over the next 10 days.

        New development:

        Yesterday a member on here (zoomer) bought a small LED USB camera and called me immediately, he picked it up in my area. We went ahead and stuffed it into the cylinders and sure enough - valve to piston contact.
        We took the timing covers off and did find the belt to be a bit loose, but the timing marks still line up perfectly. Adjusted the tensioner, belt is now as tight as it should be - marks still line up perfectly good.
        Here comes the weird part. We rotated the nuke to retard the cam about 4 degrees, assembled all the stuff and started the car for about 3 seconds. Noise was LOUDER and now with higher frequency. Returned the nuke gear to zero, started again - a bit better but still there.

        Now the question is - why did this engine cover over 3000 kms without making valve to piston contact and start doing it after a hot oil event? Both things seem to not be connected. Is it possible that the belt stretches under any load, even idling and causing the valve-piston contact, but returning to normal when engine is inop? That seems sci-fi to me, but has anyone encountered that?

        I really don't want to reassemble the engine without finding the cause of that.

        Another thing that comes to mind - the woodruf key on the crank sproket potentially could have failed, causing the timing mark to align, but the crank would be on the incorrect position.

        What I intend to do next is rotate the cam gear in the opposite direction, start briefly and if it doesn't knock/rattle, I'll check compression numbers and take it from there. Definitely will check the woodruf key on the crank sprocket, but if anyone has some other pointers, would be happy to read them.

        Thanks for the input, tim88325is and digger.​​​​​​​
        '85 Alpine Weiß 2-door with m20b30 ground up build

        Comment


          #5
          Did you check P to V during assembly?

          which valve was contacting ex or in? Advancing adds ex clearance and subtracts inlet clearance
          89 E30 325is Lachs Silber - currently M20B31, M20B33 in the works, stroked to the hilt...

          new build thread http://www.r3vlimited.com/board/showthread.php?t=317505

          Comment


            #6
            Yes, I checked during assembly, measured the clay while on the piston, it was about 2.2 mm. Only picture I have though



            I saw marks for inlet, but the camera wouldn't wiggle enough for me to check the exhausts :(
            Only thing I can think of - me being stupid and actually advancing the engine instead of retarding it. That's quite possible and only logical explanation.
            '85 Alpine Weiß 2-door with m20b30 ground up build

            Comment


              #7
              Plot twist:
              Turns out I didn't retard the engine, but myself.

              Using my memory of yesterday eve and the below link as reference, I was a dumbass and advanced the engine instead of retarding it.

              https://help.summitracing.com/app/an...ing-a-camshaft

              Attached is an image of what I think I did.

              Guess joke is on me. Hopefully my stupidity will help someone in the future.
              '85 Alpine Weiß 2-door with m20b30 ground up build

              Comment


                #8
                in fairness its not indicated on the nuke gear which way to adv and which to retard. in anycase as yuo'll be aware you probably bent the valves..

                89 E30 325is Lachs Silber - currently M20B31, M20B33 in the works, stroked to the hilt...

                new build thread http://www.r3vlimited.com/board/showthread.php?t=317505

                Comment


                  #9
                  Originally posted by gnmzl View Post
                  Turns out I didn't retard the engine, but myself.
                  Sig worthy solution.

                  Comment


                    #10
                    Originally posted by digger View Post
                    in fairness its not indicated on the nuke gear which way to adv and which to retard. in anycase as yuo'll be aware you probably bent the valves..
                    I don't see how they wouldn't have bent too. And yes, it's not indicated, that's why google provided a picture of another m20 cam gear, which is obviously wrongly indicated. Still, it's my fault for not making sure I do the right thing. Once I'm back from vacation, I'll do a leak down test and a compression test (again) and provide closure for the thread's sake.
                    Thanks for jumpstarting my brain, digger

                    Originally posted by roguetoaster View Post

                    Sig worthy solution.

                    Permission for usage granted :D
                    '85 Alpine Weiß 2-door with m20b30 ground up build

                    Comment


                      #11
                      I do leakdown rather than compression test
                      89 E30 325is Lachs Silber - currently M20B31, M20B33 in the works, stroked to the hilt...

                      new build thread http://www.r3vlimited.com/board/showthread.php?t=317505

                      Comment


                        #12
                        Time for an update, I had exactly one month to chase down this devil.
                        Here's a recap of what happened, with the help of a friend. Shoutout to member zoomer.

                        First and foremost I did a leakdown test, I had to buy the tool to do it. I did it twice for each cylinder just to be sure. All were below 15% leakage, which I hardly could believe, yet again the engine ran under 5 seconds with the advanced nuke gear. So the test showed all valves are seating good enough.
                        Next order of business was taking off the oil pan - what a pain with a scraper and a baffle.
                        Oil looked mint, not even the slightest debri in it, when I filtered it through the finest painter's filter.
                        No heat discoloration either on rods or crank, no play in any rod or whatever I could reach in there.
                        There was e tiny little smidge on the scraper, where a rod bolt had touched it ever so lightly. So small, the camera wouldn't catch it. Ok, so off with the scraper. Assembled everything, poured the oil back in and fired it up. Still clacking, right from the start, same noise again temperature independent but RPM dependent, sounds like only one element is hitting another once per revolution.
                        Next up - discovered a tiny play in the crank sprocket, so small it was unnoticable from above the engine, only when the car was on the lift could we spot it.
                        From a spare m20 - pristine sprocket with the woodruf key to go with it and the play was gone. Fire it up - same noise.

                        Listening at it again reveals the following:
                        From above: more pronounced between cyl 2 and 4
                        From beneath: more pronounced between cyl 5 and 6, but only if you listen without a screwdriver or similar to the pan. Screwdriver to pan says it's everywhere .....
                        Removing the alu cover in front of the trans and below the pan makes the sound more pronounced.
                        Flywheel doesn't have any play, but does have some slight oil drippings, that are spread by the centrifugal force starting from the flywheel bolts.

                        Now, what I am thinking - since those drippings are on the side, which faces the front of the car, is it possible, that the bolts have backed out and cause this rattle/clatter? I used brand new OEM units and torqued them down to spec, but you never know.
                        Otherwise the only thing that comes to mind is go back to the head and check every rocker arm, also warm up the engine and fire it up with the head cover off.

                        Any pointers are welcome.
                        '85 Alpine Weiß 2-door with m20b30 ground up build

                        Comment

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